Precious metals such as gold are extracted from their ores by a cyanide or ozone leaching process. On the other hand, the resulting heap leaching tailings acidic waste water, not only. The leaching of uranium from betafite sciencedirect. Kazakhstan, canada, and australia are the top three producers and together account for 70% of world uranium production.
Heap leaching is a wellestablished extractive metallurgical technology enabling the economical processing of various kinds of lowgrade ores, which could not otherwise be exploited. Acid leaching is commonly performed by agitating an ore. Dr dr groot a dissertation submitted in partial fulfilment of the requirements for the degree of master of applied sciences metallurgy department of materials science and metallurgical engineering faculty of engineering, built environment and information. In situ uranium leaching is gaining vast acceptance. Uranium leaching is more important than copper, although less amount of uranium is obtained than copper. For recovery of material occurring naturally in solution, see. For that reason, the nrc regulates in situ recovery facilities as stated above, as well as uranium mills and the disposal of liquid and solid wastes from uranium recovery operations including mill tailings. For getting one tonne of uranium, a thousand tonne of uranium ore must be handled. Uranium bioleaching process is more significant economically. All of these disciplines have made steps forward in modeling the diffusion process and all have pertinent data for the mineral processing of copper heap leaching. These general terms incorporate a large variety of design possibilitiesthere are as many methods of mining uranium as there are orebody sizes, shapes, and mineral constituents. For many decades, there has been a growing demand for heap leaching due to its environmental benefits. Heap leaching provides mining operators with a benign. Jun 29, 2019 this is much cleaner than the traditional heap leaching using cyanide.
Heap leaching is a lowcost technology used in industrial mining to recover precious metals such as gold and uranium, along with several other highly sought after metals like copper, from their primary resources ores and minerals. In the case of insitu leaching, no excavation is needed, and the process of leaching is done at the site. Radioactive metals, such as uranium are extracted by the process of acid leaching. Understanding sulphuric acid leaching of uranium from ore. In the case of heap leaching, the uranium ore is mined, placed on a pad in heaps 530 metres high and irrigated with acid or alkaline solution over many weeks, leaching uranium into the resulting pregnant liquor, which is then collected and treated to extract the uoc. National emission standards for operating mill tailings subpart w subpart w. Ironand sulfuroxidizing microorganisms are used to release occluded coppergold and uranium from mineral sulfides. T his chapter outlines the basic steps involved in mining, processing, and reclamation that might be suitable for uranium ore deposits in the commonwealth of virginia. Request pdf an integrated multiscale approach to heap leaching of uranium ore agglomerates in heap leaching, agglomeration of clay rich ores is commonly used and may prevent plugging phenomena. Methods of metal recovery by microorganisms 2 methods. In situ leach works by artificially dissolving minerals occurring naturally in a solid state. This process is dependent on the chemistry of uranium and so is independent on the type of mining system conventional, heap or insitu used. Heap leaching is a tried and tested mining technique enabling the processing of different kinds of ores which could not otherwise be exploited under viable economic conditions.
Ore is mined, crushed and dumped onto a leaching pad made from impermeable membrane with a minimum thickness of 1. Recent developments in uranium resources and production with. In the mineralization under investigation uranium does not form a definite mineral but it is hosted by apatites. However, despite much progress since it was first applied in recent times, the process remains limited by low recoveries and long extraction times. Uram conference, vienna 2014 uranium heap leaching 22 the plan 1. Bioleaching of uranium pdf united pdf comunication.
Heap leach developments on low grade ores refractory minerals deemed difficult to leach brannerite, tirich coffinite karoo sandstone acid consumption high due to presence of carbonates calcite and dolomite investigating acid ferric leaching improve rate and extent of uranium dissolution increased acid dosages during agglomeration. For the successful operation of all leaching systems, uranium must either be initially present in the more stable hexavalent state or be oxidized to that state in the leaching process. It is controlled by surface etching, diffusion, and mass transfer within the ore. Roasted uranium ores are leached of their uranium values by both acidic and alkaline aqueous solutions. However, uranium leaching from ore on a large scale is widely practiced in the usa, south africa, canada. Energy information administration 2018 domestic uranium production report iv. In some cases, uranium is extracted from lowgrade ore by heap leaching. Column leaching test was carried out for uranium ore samples obtained from a uranium insitu leaching isl mining site using 2. So we try to use continued multicolumns bioleaching in uranium to model multiheaps bioleaching as to improve the production efficiency pf reduce the production cost. Microbial leaching bioleaching, biomining environmental.
The cover pictures are of the sierra pintada uranium district in the mendoza province of argentina. Mar 09, 2010 the bacterial strain that was used in the leaching experiments was isolated from the jaduguda mine water sample. Heap leaching process is sometimes preferred instead of the in situ technique. Hydrodynamic performance critical for heap leach to.
Important metals like copper and gold are produced by this. Similar to in situ mining, heap leach mining differs in that it places ore on a liner, then adds the chemicals via drip systems to the ore, whereas in. Pdf conventional heap leaching of uranium ore in the western. This heap leaching process is applicable for the recovery of rees from. This is much cleaner than the traditional heap leaching using cyanide. Heap leaching is an industrial mining process to extract precious metals, copper, uranium, and other compounds from ore via a series of chemical. Application of united nations framework classification 2009. Uranium leaching with sulphuric acid is a complex process governed by chemical dissolution, and the oxidation of uranium. Information from the world nuclear association, the global privatesector organization that provides information on nuclear power, nuclear energy, and the role of nuclear in sustainable development.
Etango uranium project heap leach demonstration program. Table of contentsmechanism of thorium leachingprecipitate formationbacterial activitysulphuric acid consumption mechanism of uranium leaching. The common methods in the mining world are heap leaching and insitu leaching. Heap leach piles, which consist of ores that have a chemical solution applied to extract uranium. While heap leaching was introduced in the uranium industry in the 1950s, when portugal began to use the technology for extraction of uranium from lowgrade uranium ore scheffel, 2002, its an use waned as environmental concerns and low commodity prices made extraction of lowgrade material unattractive, as there were large amounts of high. Column leaching for simulating heap and insitu soil. Uranium, heap leaching tailings, neutralization, porosity. Recovery of uranium from uranium residue by alkaline leaching by bundjoko kweto supervisor. Pdf conventional heap leaching of uranium ore is neither a new concept historically in the united states, nor is the idea unfamiliar on a. Particular reference is made to the geochemical conditions at crownpoint.
Purification or separation of uranium in carbonate systems. The front cover shows a general view of the mining area, and the back cover installations for heap leaching. The uranium bearing pregnant solution can then be recovered through production wells. Heap leaching of gold ore started to gain promenence in the late 1960s when it was applied on a large scale to low grade ores that were uneconomic to procees by conventional tank leach methods. A brief note on the heap leaching technologies for the.
It was discovered in the mid s that microorganisms use metals in the cell. This is because the recovery of uranium in much higher with heap leaching. Preconcentration by screening, gravity separation and radiometric sorting can potentially reduce the mass flow to the downstream leach and recovery plants. Pdf a brief note on the heap leaching technologies for the. The cost of the heap leaching process is low, making this process an.
Besides copper and uranium, bioleaching technique is also used for extraction of other metals such as nickel, gold, silver, cobalt, molybdenum and antimony. Efficiency of bioleaching was studied by varying parameters like pulp density and initial ferrous concentration as source of energy. An integrated multiscale approach to heap leaching of. Further enhancing project knowledge designed, permitted, constructed and successfully commissioned large scale demonstration plant. Uranium leaching uranium leaching is more important than copper, although less amount of uranium is obtained than copper. The influence of uranium mineralogy and the lithology and behaviour of the host rocks means of effecting capital and operating cost reductions, particularly for lower grade deposits flowsheet options for acid leaching and purification flowsheet options for alkaline leaching and purification impact of salinity on the process flowsheet.
A brief note on the heap leaching technologies for the recovery of. Recent developments in uranium resources and production. Acid leaching is sometimes also referred to as heap leaching because the leaching process can be performed on large heaps of uranium ore that have been collected from mines. Heap leaching of ore is becoming more important as a cost effec tive means of metal extraction. Microbial leaching of copper has been widely used in the usa. The activity ratio of the two uranium isotopes in the pregnant leach solution was measured by. The leaching agent alkaline, or sulfuric acid is introduced on the top. United states environmental protection agency office of radiation and indoor air 6608t epa 450f17005. For oxide ores, recovery only slightly reduced with. A comparison of the uranium recovery from lowgrade ore by. During 1952 and 1953, the plant at urgeirica started a uranium heap leaching process on a commercial scale.
Of late heapleaching methods for extraction of uranium from small deposits of highgrade ores and other deposits of lowgrade ores in outofthe way localities. The first use of cyanide for leaching of gold and silver ores was in england in 1887 by j. Uranium recovery by heap leaching methods in arizona new mexico wyoming uranium energy corp 6100 indian school rd ne, suite 225 albuquerque, nm 87110 505 830. Insitu leaching, also called insitu recovery or solution mining, is a mining process used to recover minerals such as copper and uranium through boreholes drilled into a deposit, in situ. In situ microbial leaching is greater acceptance since it eliminates the expense of moving vast amounts of material. The ore can be processed as coarse rock, normally referred to as a dump leach, or as a crushed ore in a heap leach. Based on the current understanding of uranium deposits in the commonwealth of virginia, extraction of uranium ore would use openpit mining, or underground mining, or a combination of both. An integrated multiscale approach to heap leaching of uranium. Currently, the nrc regulates active uranium recovery operations in new mexico, and nebraska.
The leaching solution is injected into the ore formation to dissolve uranium. Leaching in columns simulates percolation leaching because the conditions are very similar to those in the heap 5. United states environmental protection agency office of radiation and indoor air 6608t epa 450f17005 april 2017. Neutralization processing and study of dynamic of acidic. In situ leaching isl, solution mining, or in situ recovery isr involves dissolving uranium in the ground and pumping the solution to the surface where the minerals can be recovered. Introduction in china, acid heap leaching technology has been used increasingly in hard rock uranium mines. Pdf heap leaching is a lowcost technology used in industrial mining to recover precious metals such as gold and uranium, along with several other. Other important uranium producing countries in excess of 1,000 tons per year are niger, russia, namibia, uzbekistan, china, the. In the usa 200 tonnes of copper is recovered per day. Bioleaching of lowgrade uranium ore using acidithiobacillus.
Wmc copper uranium division copper ore heap leaching. Phosphate fertilizers as a proliferationrelevant source. The leaching process in mining is carried out either as heap leaching or insitu leaching. The latter allows simulation of the full scale operation of heap leach pads, as defined in the dfs. Heap leaching and its application to copper, uranium. Characterization of the leaching properties of a uranium. The process initially involves the drilling of holes into the ore. Recovery uranium from uraniumbearing waste ore using heap. In situ leach isl mining of uranium june 2009 z most uranium mining in the usa and kazakhstan is now by in situ leach methods, also known as in situ recovery isr. Modern day heap leaching, which has a relatively low level of energy consumption, is for example. Kinetics of uranium leaching the typical leach curve shown in figure 1 indicates that the initial leaching rate is fast but that it decreases with time, and that some of the uranium is very slow leaching or characterization of the leaching properties of a uranium leaching pulp by j. Testing confirms the simple chemistry and efficient leaching nature of the granite host rock and uranium mineralisation. For uranium ore deposits, the choice of mining methods and processing options is very depositspecific and dependent on many variables such as the quality and quantity of the ore, the shape and depth of the ore deposit, site.
Uranium is commonly understood as a material storing a huge energy and its only commercial application is as nuclear fuel. Some supporting data from studies using alkaline leach for remediation of uranium. It is observed that the efficiency of bioleaching was 49% at 10% pulp density wv and initial ph 2. Pdf heap leaching technologycurrent state, innovations. Nonetheless, heap leaching has also been used to extract uranium from ore at conventional mills, and ionexchange procedures have been used to separate uranium from the liquid extract at both conventional mills and isr facilities. The chemistry of the leaching process revolves around oxidation of the uranium compounds, which is typically achieved using manganese dioxide mno 2, sodium chlorate. Bicarbonate leaching of uranium unt digital library. Uranium ore leaching pregnant leach liquor ion exchange solvent extraction precipitation. At the same time, the first modern copper heap leach operation may have been the bluebird copper oxide mine in 1968 bartlett, 1998, followed in the early 1970s by a few other small operations in the western united states. Oct 28, 2015 not unlike insitu leach mining, heap leach mining is a process whereby uranium, copper and other precious metals are extracted from ore with a chemical solution. The hp2 test example involving leaching of uranium tailing is adapted here to show the applicability of vs2drt for such cases. This method has been tested for uranium recovery since 1975 taylor, 1979. After 146 days of performance, the slag uranium leaching rate was 55. Heap leaching experiencebased approach to successful heap.
Cement, limestone or fly ash are used for heap leaching gold ores with cyanide, and could be considered for alkaline heap leaching of uranium ores or ammonia leaching. The reagents used and the chemistry of leaching are metal. Heap leaching leaching is a technology to extract pre cious metals, copper, uranium or other combinations from ore via chemical reac tions that absorb specific minerals and then reseparate them after their division from other earth materials. Studies on uranium recovery from a uranium bearing phosphatic sandstone by a combined heap leaching liquidgel extraction process. This may be done if the uranium contents is too low for the ore to be economically processed in a uranium mill. Uranium deposit mineralogy and associated chemistry there are numerous types of uranium minerals in existence, the simplest form being uraninite.
The study has proven that recovery uranium from uranium bearing waste ore using heap bioleaching is feasible. Although usually acidic mine waters were used for ore processing,4 billion liters of freshwater. Heap leaching is an industrial mining process used to extract precious metals, copper, uranium, and other compounds from ore using a series of chemical reactions that absorb specific minerals and reseparate them after their division from other earth materials. While it is possible to directly precipitate uranium from. Application of united nations framework classification 2009 unfc2009 for uranium resources uranium ore processing i. In addition, in situ leaching of uranium is more sensitive to good engineering management and attention to detail. Heap leachionexchange operations involve the following process.
Another critical factor was the supply of water for the leaching heaps. Heap leach depths have increased to more than 500 ft of ore depth from only 50 to 65 ft a decade ago. Mineral beneficiation by heap leaching technique in mining. Some supporting data from studies using alkaline leach for remediation of uranium contaminated. Acid leaching of agglomerated ore stacked to 5m occurs in four 2m x 2m x 6m leach cribs. Industrialscale experiment on bacterial heap leaching of uranium ore 262 fan baotuan, liu jian, meng yunsheng, niu yuqing. In addition to the cribs, eight 5m high columns as shown below with an internal diameter of 0.
Uranium mining is the process of extraction of uranium ore from the ground. The worldwide production of uranium in 2015 amounted to 60,496 tonnes. Studies on uranium recovery from a uraniumbearing phosphatic. The goal of the present study was to compare uranium recovery by bioleaching and acid leaching in identical columns under similar process conditions for the same material. Heap leaching is an extraction process by which chemicals usually sulfuric acid are used to extract the economic element from ore which has been mined and placed in piles on the surface. The use of ionexchange recovery in the copper industry is not widesprea d. Heap leaching is generally economically feasible only for oxide ore deposits. Vs2drt is a new reactive transport model for vsaturated porous media. Simulation of uranium tailing leaching using vs2drt. Application of united nations framework classification.